Chlorosulfonated polyethylene polymers are special elastomers excellent in ozone resistance, weather resistance, heat resistance, oil resistance, and chemical resistance, and these excellent characteristics have been taken advantage of in extruded articles, such as wire coatings and hoses, or calendared articles, such as coated fabric.
In recent years, higher performance properties have been required of rubber parts, particularly automobile parts, to stand use under very severe conditions. Chlorosulfonated polyethylene polymers have also been demanded to have improved performance, particularly ozone resistance for use, e.g., as coating materials of various automotive hoses.
Known methods for improving ozone resistance include compounding of a vegetable oil having an unsaturated bond. However, a vegetable oil is extracted on contact with fuel oil or grease to reduce its effect. JP-A-63-57654 (the term "JPA" as used herein means an "unexamined published Japanese patent application") proposes a chlorosulfonated polyethylene polymer composition free from permanent set and excellent in ozone resistance, comprising a chlorosulfonated polyethylene polymer having incorporated therein an amine maleimide compound, nickel dithiocarbamate, a metal oxide, and a polysulfide compound, but the effect of improving ozone resistance is still insufficient.